Simplified environmental atmosphere measuring apparatus

ABSTRACT

When adsorbed gas is analyzed after metal, ceramics or metallic salt has been left in an environmental atmosphere for a predetermined period of time, an average concentration of specific gas over a long period of time can be accurately measured with an inexpensive small apparatus. Especially, porous metal or ceramics (transition metal oxide) are excellent in selective adsorption properties for NO x , porous ceramics (rare earth element oxide) are excellent in selective adsorption properties for CO 2 , and a specific chloride such as copper chloride and silver chloride is excellent in selective adsorption properties for SO 2 . A test kit accommodating such test pieces in a case, a protective case for the test kit to put the test kit into practical use, an umbrella and a forced air blowing unit are also disclosed.

This application is a division of application Ser. No. 08/178,357, filedJan. 4, 1994, which is a CIP of parent application Ser. No. 08/140,153,filed Nov. 4, 1993, now abandoned, which is a 37 of PCT JP93/00277,filed Mar. 4, 1993.

TECHNICAL FIELD

The present invention relates to a simplified environmental atmospheremeasuring method and apparatus, and more particularly relates to asimplified environmental atmosphere measuring method, a measuring kitand a protective case for test pieces, which is capable of measuring theatmosphere in an environment when simple test pieces are left in theenvironment to be measured and then collected after a predeterminedperiod of time has passed and then the gas to be tested is measured.

BACKGROUND TECHNIQUE

Recently, NO_(x), CO₂, SO₂ and the like existing in the atmosphere havebecome a serious environmental problem. The cause of NO_(x) is exhaustgas discharged from automobiles and factories. In the natural world, theconcentration of NO₂ and NO is several ppb. On the other hand, in bigcities, the concentration of NO₂ and NO is 50 ppb at the maximum, whichcauses a serious social problem. The situation is the same in the caseof CO₂. Further, acid rain causes a serious problem. Air pollutioncaused by SO₂ gas contained in the combustion gas discharged fromfactories could be one of the factors causing acid rain.

Recently, the size and weight of electronic apparatuses such aselectronic computers, for example, personal computers, word processors,facsimiles, telephones, and notebook-type personal computers, tend to bereduced. In these small electronic apparatus, the problem of corrosionoccurs. Conventional large-sized electronic computers are installed inair-conditioned environments, so that the problem caused by corrosionrarely occurs. However, small-sized electronic apparatuses are used inall environments. Therefore, not only H₂ S, Cl and humidity but alsoNO_(x), SO₂ and the like might affect those electronic apparatus.

The present invention provides a method by which these gases are simplycollected and analyzed so that the environment can be monitored.

At present, there is provided a method to monitor the concentration ofNO_(x) for which an expensive large-sized automatic measuring apparatusis used. By the above method, the concentration of NO_(x) is measured inthe following manner: Into a Saltzman reagent in which phosphoric acid,sulfaninilic acid, and Nl naphthyl ethylene diamine hydrochloride aredissolved in distilled water, a predetermined amount of air containingNO_(x) is sent by an air pump. When this reagent reacts with NO_(x), thecolor of the reagent changes to pink. The higher the concentration ofNO_(x) in the reagent is, the denser the color of pink becomes. Next,the reagent is exposed to light, and the concentration of the coloringliquid is measured by a value of the transmission factor.

However, this method is disadvantageous in that: it is not possible tomeasure the concentration of NO_(x) at an arbitrary position; andfurther the period of time to collect data is so short that it isnecessary to analyze a large amount of data to know an averageconcentration over a long period of time. Therefore, this method cannotbe applied to many cases.

There is provided a method to monitor the concentration of CO₂ for whichan expensive large-sized automatic measuring apparatus and asemiconductor sensor are used. It is not possible to apply thismeasuring method at an arbitrary position. Further, the period of timeto collect data is so short that a large amount of data must be analyzedto provide an average concentration over a long period of time. In orderto measure the concentration of CO₂ gas, a nondispersive infraredanalyzer (NDIR) and a gas chromatograph (GC) are commonly used. Intothose apparatus, the gas to be measured is introduced, and relativedetermination is performed in accordance with the absorption rate foundfrom the light absorption coefficient. However, these methods can beapplied to only limited locations, that is, in cities, where themeasuring apparatus can be easily conveyed and a power source can beeasily provided. In a mountainous area, forest or jungle, it isdifficult to use these apparatuses.

In order to measure the concentration of SO₂ gas, the following methodhas been known: An absorption solution is put in a collecting bottle,and the bottle is plugged with a cap having a bubbler. When the air inthe collecting bottle is sucked by a collecting pump, the environmentalair is introduced to the absorption solution, and SO₂ gas in the air istrapped by the absorption solution in accordance with the methodprescribed by JIS K-0103. After that, the absorption solution ischemically analyzed, and the obtained result is converted into theconcentration of gas.

According to the aforementioned method, it is possible to collect onlysulfur oxide so that the concentration of sulfur oxide can be accuratelyprovided. However, an operator skilled in operating the entire apparatusis required for normally operating the power source to drive the airpump and for normally operating the collecting device. Therefore, thelocation and time for sampling are limited.

Further, the following measuring method has been known: After a filterpaper has been soaked in a water solution of potassium carbonate, it isair dried. Then, the filter paper is left in an environment so as tocollect SO₂ gas, which is chemically analyzed and the obtained result isconverted into the concentration. According to this alkaline filterpaper method, only the filter paper must be set in a location where theenvironment is measured, so that the gas collecting work is simple.However, H₂ S is collected in the form of SO₃. Therefore, this method isessentially disadvantageous in that it is impossible to discriminatebetween SO₂ and H₂ S.

Accordingly, it is desired to provide a method to monitor the averageconcentrations of NO_(x), CO₂ and SO₂ at an arbitrary location over along period of time.

In order to accomplish the similar object, the present applicant(Fujitsu Co., Ltd.) has developed and disclosed a method in JapaneseUnexamined Patent No. Sho. 63-305232, by which the concentration ofcorrosive gas is monitored with a metallic test piece. However,according to this method, it is difficult to collect NO_(x) and CO₂, andfurther the obtained result is not accurate. Moreover, it is difficultto discriminate between SO₂ and H₂ S. Therefore, the accuracy cannot beimproved.

It is desirable to improve the handling properties of test pieces andalso to eliminate the causes to disturb the measuring condition when thetest pieces are left in various measuring environments.

It is an object of the present invention to provide a method and meansby which the average concentrations of NO_(x), CO₂ and SO₂ gases can besimply and accurately monitored in an environmental atmosphere at anarbitrary location with an inexpensive and small-sized apparatus.

DISCLOSURE OF THE INVENTION

In order to accomplish the above object, the present invention is toprovide a method for measuring an environment characterized in that: atest piece made of metal, ceramics or metallic salt is set in anenvironmental atmosphere to be measured; and after a predeterminedperiod of time has passed, NO_(x), CO₂ or SO₂ adsorbed by the test pieceis subjected to quantitative analysis so as to determine theconcentration of NO_(x), CO₂ or SO₂ in the environmental atmosphere.

In this specification, it should be understood that the terminology of"adsorption" includes not only physical adsorption but also chemicaladsorption in which gas is collected through a chemical reaction.

Specifically, when the concentration of NO_(x) gas is measured, testpieces made of porous metal or ceramics are used. Alternatively, testpieces made of metal or ceramics, around which metallic particles orceramic powder is attached, are used. More specifically, it ispreferable that the porous or particulate metal is one of copper,silver, platinum, rhodium, ruthenium, palladium, iridium and nickel, andit is also preferable that porous or particulate ceramics is one of SiO₂--Al₂ O₃, YBa₂ Cu₃ O_(x), CrO₂, Cr₂ O₃, Fe₂ O₃, Co₂ O₃, SnO₂, CoAl₂ O₄,CuO, Al₂ O₃, and MgO (generally, oxide of transition metals).Alternatively, the test piece may be made of porous metal or ceramics,the voids of which are filled with triethanolamine having a function toabsorb NO_(x) gas.

To measure the concentration of CO₂ gas, porous rare earth metal oxideis used, for example, a test piece is used which is made of one of La₂O₃, Ce₂ O₃, Pr₂ O₃, Nd₂ O₃, PM₂ O₃, Sm₂ O₃, Eu₂ O₃, Gd₂ O₃, Tb₂ O₃, Tb₃O₇, Dy₂ O₃, Ho₂ O₃, Er₂ O₃, TM₂ O₃, Yb₂ O₃, and Lu₂ O₃.

To measure the concentration of SO₂ gas, a chloride of a metal, whichmetal has a free formation energy of chloride larger than a freeformation energy of sulfate, for example, copper chloride or silverchloride is used.

Of course, two or more test pieces may be concurrently used in themonitoring work. Also, the test pieces may be used together withmetallic test pieces (copper, silver, aluminum, iron and 52 alloy orsome of these) for monitoring corrosive gas as disclosed in JapaneseUnexamined Patent No. Sho. 63-305232. Alternatively, the test pieces maybe used together with other test pieces (for example, inorganicsubstance such as platinum, gold and refractory metals) may be used, andfurther organic substance may be also used.

Also, the present invention is to provide a measuring kit to determinethe concentration of NO_(x), CO₂ or SO₂ contained in an environmentalatmosphere, the measuring kit including: a test piece made of metal,ceramics or metallic salt to selectively adsorb NO_(x), CO₂ or SO₂ gasin an environmental atmosphere; and a case used for leaving the testpiece in the environmental atmosphere to be measured.

The test piece used for the measuring kit may be a combottleation of theaforementioned test pieces for monitoring NO_(x), CO₂ or SO₂ andmetallic pieces (or organic substance) disclosed in Japanese UnexaminedPatent No. Sho. 63-305232 described before.

According to the present invention, a test piece protective case forenvironmental investigation is provided so as to be preferably used forthe aforementioned measuring kit, the test piece protective caseincluding: a base body to hold a test piece made of metal, ceramics ormetallic salt for determining the concentration of an environmentalatmosphere; and a cover to cover the test piece, the cover beingattached to the base body, wherein a portion of the cover covering amain surface of the test piece or a portion of the base body istransparent so that the main surface of the test piece can be observedfrom the outside, and an entrance through which the atmospheric gaspasses is formed in a portion of the cover or the base body which doesnot cover the main surface of the test piece.

The use of the test piece protective case for environmentalinvestigation is not limited to a test piece for monitoring NO_(x), CO₂or SO₂ gas, but it can be effectively applied to a test piece protectivecase for a general environmental investigation.

A preferable embodiment is composed in the following manner: a testpiece is placed so that a main surface of the test piece can be locatedin parallel with a bottom surface of the base body; a cover made oftransparent resin is attached to the base body so that the main surfaceof the test piece can be covered; entrances through which theenvironmental gas passes are formed on both sides of the main surface ofthe test piece so that the atmospheric air can flow in parallel with themain surface of the test piece; and a collar is provided forfacilitating a flow of the atmospheric air into the atmospheric gasentrance. Further, the preferable embodiment includes an umbrella toshelter the device from rain and snow. Furthermore, the preferableembodiment includes a means to forcibly feed the environmental gas tothe main surface of the test piece.

It is preferable that the apparatus is constructed so that theprotective case can be used as it is even when the umbrella and theenvironmental gas feed means are provided. A fan is conveniently usedfor the environmental gas feed means. When the environmental gas feedmeans is driven by a solar battery, the power transmission means can beomitted, which is advantageous in the case where the apparatus is usedin a remote place.

Further, the present invention provides an umbrella for the test pieceprotective case, including: a sample fixing portion to accommodate theprotective case for the test piece to measure the environmental gas; andan umbrella portion to cover the sample fixing portion for protectingthe test piece from rain and snow, wherein the test piece protectivecase accommodated in the sample fixing portion is provided with an airport through which air passes. A preferable embodiment is constructed inthe following manner: the umbrella portion is composed of a conicalsheet; the sample fixing portion is composed of a cylindrical portionformed of a sheet, in which a sample is accommodated, and also composedof a plurality of arm portions extending from a top of the conicalportion; and the sample fixing portion is attached to the umbrellaportion through the arm portions.

Also, the present invention provides a forced-air-blowing unit for thetest piece protective case including: an air inlet and an air outlet; asample accommodating portion and a fan provided in a communicated spacebetween the air inlet and the air outlet, the sample accommodatingportion accommodating the protective case for the test piece to measurethe environmental gas; and an air flow from the air inlet to the airoutlet is caused by the fan. It is preferable that the fan is driven bya battery such as a dry battery or a solar battery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic illustration for explaining the principle of themethod of the present invention, wherein the explanation is maderelating to NO_(x).

FIG. 1B is a schematic illustration for explaining the quantitativeanalysis performed by an X-ray electron spectroscopy device (XPS).

FIG. 2 is a schematic illustration showing the circumstances (measuringkit) in which test pieces of the present invention are accommodated.

FIGS. 3A to 3E are schematic illustrations showing in detail the samemeasuring kit as that shown in FIG. 2.

FIGS. 4A to 4D are views showing an umbrella for the measuring kit indetail.

FIGS. 5A and 5B, FIGS. 6A and 6B, FIGS. 7A to 7C are respectivelyschematic illustrations showing various embodiments of the accelerationtest device to be combined with the measuring kit.

FIGS. 8A to 8C are schematic illustrations showing an NO_(x) measuringtest piece and its inside.

FIG. 9 is an infrared ray spectral diagram in which NO_(x) adsorbed to aporous copper test piece is analyzed.

FIGS. 10 and 11 are diagrams showing the X-ray intensity of oxygen (O)and nitrogen (N) contained in a copper test piece measured byfluorescence X-ray analysis.

FIG. 12 is a diagram showing a relation between a period of time inwhich a copper test piece is left in NO_(x) gas, and fluorescence X-rayintensity of adsorbed oxygen (O) and nitrogen (N).

FIG. 13 is a schematic illustration showing the internal structure of atest piece made when copper particles and fine ceramics powders werekneaded and fired.

FIG. 14 is a schematic illustration of a test piece made when a largenumber of holes are formed in a copper piece.

FIG. 15 is an XPS analysis spectral diagram obtained after CO₂ wasadsorbed to a porous Tb₂ O₃ test piece.

FIG. 16 is a diagram showing a relation between a period of time inwhich a porous Tb₂ O₃ test piece was left in CO₂ atmosphere, and CO₂intensity.

FIG. 17 is a diagram showing a relation between an adsorption amount ofCO₂ in the case where various types of rare earth metal oxides wereused, and a period of time in which the test piece was left.

FIG. 18 is a diagram showing an analytical curve of SO₂ measurementconducted by silver chloride.

FIGS. 19A to 19C are diagrams showing the results of analysis ofcorrosion products produced on test pieces in the case where themeasuring kits were placed under the eaves, in the yard (with anumbrella), and in the yard (without an umbrella).

FIG. 20 is a diagram showing an amount of sulfur (S) reacted with asilver test piece in the case where air was sent to the silver testpiece at a predetermined speed.

FIGS. 21 and 22 are diagrams showing a relation between a period of timein which a test piece was left, and an amount of sulfur reacted with thetest piece in the case where the acceleration devices shown in FIGS. 5A,5B and FIGS. 6A, 6B were used.

FIGS. 23 and 24 are diagrams showing the variation of an amount ofsulfur (S) reacted with a test piece in the case where the wind speedwas changed in the acceleration device shown in FIGS. 7A to 7C.

FIG. 25 is a color photograph of a table of color samples for detectinggases in an environment:

FIGS. 26 to 29 are color photographs of a series of color or appearancesamples;

FIG. 30 shows the amount of sulfur in a silver test piece placed in anenvironment with a certain humidity;

FIG. 31 is a cross-sectional view of a test piece having a coating ofindium oxide and/or tin oxide;

FIGS. 32 and 33 show the effect of the ITO coating on the amount ofsulfur in a silver test piece placed in a dry environment; and

FIG. 34 shows the effect of the ITO coating on the amount of nitrogen ina brass test piece placed in a dry environment.

MOST PREFERRED EMBODIMENT OF THE INVENTION

Monitoring of NO_(x) gas (1)

FIG. 1A is a schematic illustration showing the principle of the presentinvention, relating to the measurement of NO_(x) gas. According to thepresent invention, nitrogen oxide in an environment is collected andanalyzed in the following manner: A porous metallic or ceramic testpiece 1 capable of adsorbing nitrogen oxide is placed in an environmentto be measured for a predetermined period of time; nitrogen oxide 3 isadsorbed and collected by the surfaces of the metallic or ceramicparticles 2 in the porous structure of the test piece 1; and theadsorbed nitrogen is subjected to quantitative analysis by means of,e.g., fluorescent X-ray spectroscopy so that an amount of the adsorbednitrogen can be determined. In this case, the nitrogen oxide is onlyadsorbed by the test piece, or the nitrogen oxide reacts with metal orceramics of the test piece so as to be fixed. Either will do in thepresent invention. The environmental atmosphere nitrogen oxide contentcan be judged according to the result of the analysis.

The quantitative analysis of nitrogen and the like can be also made withan X-ray electron spectroscopy device (XPS), and the circumstances areshown in FIG. 1B.

FIG. 2 shows an example of the apparatus used for setting the testpieces in an environment. An appropriate number of test pieces 8 areaccommodated in a transparent container 7, and an opening 9 is formed onthe side of the transparent container 7 so that the outside and insidecan be communicated. One of the test pieces 8 is a test piece formeasuring nitrogen oxide according to the present invention, and othertest pieces are made of metal such as copper, silver and aluminum. Thesemetallic test pieces are used for detecting various substances in anenvironment (For example, hydrogen sulfide, sodium chloride and moistureare detected.). This container 7 will be described in detail later.

Nitrogen oxide has a relatively low reactivity. Therefore, nitrogenoxide adsorbed onto a surface of simple metal or ceramics is easilyscattered, so that the adsorbed amount of nitrogen oxide is notsufficient for measurement.

However, the present inventors employed porous test pieces so as toadsorb nitrogen oxide. They found that the porous test pieceseffectively adsorbed a sufficient amount of nitrogen oxide for detectionin an environment.

Examples of usable metallic materials to adsorb nitrogen oxide in thepresent invention are: copper, silver, platinum, rhodium, ruthenium,palladium, iridium and nickel. Preferable ceramic materials are: SiO₂--Al₂ O₃ (especially SiO₂ -xAl₂ O₃ (x≦0.15)), YBa₂ Cu₃ O_(x), CrO₂, Cr₂O₃, Fe₂ O₃, Co₂ O₃, SnO₂, CoAl₂ O₄, CuO, Al₂ O₃, and MgO.

These materials are excellent in their performance to adsorb and fixnitrogen oxide. Especially when oxide ceramics are in a condition ofoxygen deficiency, their fixing capacity for nitrogen oxide ispreferably improved. In order to make oxide ceramics oxygen deficient,for example, oxide ceramics may be subjected to heat treatment in areducing atmosphere.

In order to make porous test pieces, metallic particles or ceramicpowder may be simply molded (for example, pressed). Alternatively,metallic particles or ceramic powder may be fired at a relatively lowtemperature so as to sinter to a porous body of low density.

Alternatively, voids in a piece of porous metal or ceramics may befilled with fine ceramics or metallic powder. For example, fine ceramicpowder is attached onto the surface of metallic powder, and thismetallic powder is molded or fired to form a porous test piece. In thisway, a test piece containing finer ceramics having increased specificareas can be provided as compared with a case in which ceramic particlesare simply molded or sintered. Alternatively, a solid metallic orceramic piece may bear fine ceramic or metallic powder. For example, asolid metallic piece or a metallic sheet may be mechanically processedto form protruded and recessed portions so as to bear ceramic powder.Alternatively, holes or through-holes may be formed in the solidmetallic piece or the metallic sheet so as to bear ceramic powder.Alternatively, after a porous sintered metallic or ceramic piece hasbeen made, the sintered piece may be impregnated with fine ceramic ormetallic powder.

When triethanolamine (C₂ H₄ OH)₃ N is charged into the voids in a porousmetallic or ceramic piece, the same effect can be provided sincetriethanolamine absorbs nitrogen oxide.

Metallic or ceramic powder to make a test piece is not necessarilylimited, however, it is preferable to use powder, the particle size ofwhich is not more than 200 μm. The reason is as follows. When theparticle size is larger than 200 μm, bonding or necking hardly occurs inthe case of sintering performed at low temperature, so that sufficientstrength cannot be provided. When the particle size is smaller than 30μm, bonding or necking tends to occur even in the case of sinteringperformed at low temperature, so that there is a possibility that thedensity is increased and the surface area is lowered. For the reasonsdescribed above, in general, it is preferable to use metallic or ceramicpowder, the particle size of which is in a range from 30 to 200 μm. Aslong as the density of the porous portion of the test piece can belowered, metallic or ceramic particles, the particle size of which issmaller than 30 μm, may be used. Powder of small particle size ispreferable, because the smaller the particle size is, the more thespecific area is increased. In an embodiment to coat, charge or bear theaforementioned fine ceramic powder, very fine ceramic powder, theparticle size of which is 0.05 to 5 μm, may be used.

In the case of porous metal, the density of a test piece is preferablynot more than 7 g/cm³, and in the case of porous ceramics, the densityof a test piece is preferably not more than 2 g/cm³. In a test piece inwhich metal and ceramics are compounded, the density is determined inaccordance with the compound ratio. When the density is maintained atthe values described above, a test piece can be provided, the surfacearea of which is large, that is, NO_(x) gas is easily adsorbed to thetest piece. Therefore, quantitative analysis can be performed with highsensitivity.

In this connection, the amount of nitrogen oxide adsorbed onto this testpiece is determined by the product of gas concentration and time.Therefore, when the test piece is left over a long period of time (forexample, for a month) and collected to analyze it with variousanalyzers, an average gas concentration at the location can be easilydetermined.

That is, according to the present invention, a small inexpensive andhandy monitoring apparatus can be easily provided, thereby an averageconcentration of NO_(x) gas can be measured over a long period of timeat a location.

Monitoring of CO₂ gas

Monitoring the concentration of CO₂ gas is performed in the same manneras that of NO_(x) gas. However, test pieces capable of selectivelyadsorbing CO₂ gas are used. Specifically, a ceramic, made to be porous,and with its density reduced, is used. Especially, porous rare earthmetal oxides are used, for example, test pieces are used which are madeof one of La₂ O₃, Ce₂ O₃, Pr₂ O₃, Nd₂ O₃, Pm₂ O₃, Sm₂ O₃, Eu₂ O₃, Gd₂O₃, Tb₂ O₃, Tb₄ O₇, Dy₂ O₃, Ho₂ O₃, Er₂ O₃, Tm₂ O₃, Yb₂ O₃, and Lu₂ O₃.The inventors have found that CO₂ gas in an environment can beeffectively adsorbed by the test piece made of the above oxide so as todetermine an amount of CO₂ gas.

In this case, the porosity, pore size and particle size of the poroustest piece can be determined in the same manner as those of themonitoring test piece for NO_(x) gas.

When an amount of CO₂ gas is determined by an X-ray electronspectroscopy device (XPS), a peak for C existing in the range 285 to 290eV is separated, and a ratio of the surface area of the peak for Ccorresponding to CO₂ based on the surface area of the peaks for C isfound. Also, a quantitative value of C is found from the entire area ofthe C peaks and the peak area of the entire elements to be detected. Theproduct of this quantitative value of C and the area rate corresponds tothe quantitative value of CO₂.

Monitoring of SO₂ gas

Monitoring of SO₂ gas is essentially the same as that of NO_(x).However, test pieces which selectively adsorb and react with SO₂ areused. When it is necessary to discriminate between H₂ S and SO₂, theselectivity of SO₂ is important. Therefore, the following investigationwas made.

Under the natural condition, the lower the standard formation energy ofa substance, the more stably the substance exists. The inventors tooknotice of this principle, and sought a substance that can be stabilizedin the form of sulfate. As a result of the investigation, it has beenfound that the following sulfates are stable.

    ______________________________________                                                   Standard Formation Energy                                          Sulfate                               (ΔGf°/kjmol.sup.-1)        ______________________________________                                        Ag.sub.2 SO.sub.3                                                                        -411.3                                                             Ag.sub.2 SO.sub.4                                                                                             -618.48                                       CuSO.sub.4                              -660.90                               ______________________________________                                    

Next, a compound of which the standard formation energy is higher thanthat of the above sulfates may be selected. However, depending on acompound, there is a possibility that the compound reacts with H₂ S, NO₂and O₂ in an environment to generate sulfide, nitrate and oxide. Thiscould be a factor to interrupt the collection of only SO₂. Therefore,the standard formation energy of sulfide, nitrate and oxide of copperand silver was investigated. The result of the investigation is shown infollowing table.

    ______________________________________                                        Sulfide, Oxide, and                                                                         Standard Formation Energy                                       Nitrate         (ΔGf°/kjmol.sup.-1)                              ______________________________________                                        Ag.sub.2 S    -39.46                                                          Ag.sub.2 O      -11.21                                                        AgNO.sub.3      -33.47                                                        Cu.sub.2 S      -86.20                                                        CuO              -128.12                                                      Cu(NO.sub.3).sub.2                                                                           -102.9                                                         ______________________________________                                    

As can be seen from the result, a compound of which the standardformation energy is lower than that of sulfide, oxide and nitrate may beselected. Accordingly, the following compounds were selected as thestandard formation energy is higher than that of sulfate and lower thanthat of sulfide, nitrate and oxide.

    ______________________________________                                                    Standard Formation Energy                                         Compounds                    (ΔGf°/kjmol.sup.-1)                 ______________________________________                                        AgCl        -109.80                                                           CuCl                              -120.9                                      ______________________________________                                    

Only a few sulfates and compounds are listed in the above table. Ofcourse, other sulfates and compounds satisfying the aforementionedconditions can be applied.

When test pieces, in which copper chloride CuCl and silver chloride AgClare used, are prepared in such a manner that the surfaces of copper andsilver are chlorinated in an atmosphere of chlorine to form layers ofCuCl and AgCl, these test pieces are preferably used from the viewpointsof improvements in handling properties and adhesion properties of CuCland AgCl layers.

Measuring Kit

The above test pieces, excellent in selective adsorption of NO_(x), CO₂and SO₂, are accommodated in a case and left in an atmosphere to bemeasured. Therefore, a measuring kit in which at least one test piece isaccommodated in the case is usefully applied for measuring NO_(x), CO₂or SO₂ gases in an environment.

As described above, this measuring kit is applied to the test pieces formeasuring the concentrations of NO_(x), CO₂ and SO₂, and further appliedto the metallic test pieces disclosed in Japanese Unexamined Patent No.Sho. 63-305232 and other test pieces (test pieces made of organicsubstances are included), wherein these test pieces may be accommodatedin the measuring kit in combination.

Protective Case

(1) In order to accomplish the object of the present invention, the caseof the measuring kit accommodates test pieces so that the test piecescan be easily left in an environment to be measured. In the case where atest piece for measuring corrosive gas is accommodated in the case, thecorrosive gas comes into contact with the test piece, and then the testpiece starts corroding, so that the color of the test piece is changed.Therefore, it is preferable that the change of color can be observedfrom the outside of the protective case. When an operator's handscarelessly comes into contact with the test piece or water droplets areattached to the test piece, the test piece will be corroded by a factornot relating to the object of measurement. Accordingly it is preferableto protect the test piece with a protective cover of the protectivecase.

When the test piece is covered in the aforementioned manner, it isnecessary to provide an entrance to feed the outside atmosphere onto thesurface of the test piece. Therefore, the entrance for the atmosphere isprovided in a portion of the cover not covering a main surface of thetest piece.

(2) With reference to FIGS. 3A to 3E, a preferable protective case willbe explained as follows. FIG. 3B shows a base of the protective case.FIG. 3C shows a cover to be engaged with a base of the protective case.FIG. 3A is a schematic illustration showing a condition in which thecover is engaged with the base. Each of FIGS. 3D and 3E shows a sectionof the center of the protective case. FIG. 3D shows a cover. FIG. 3Eshows the base.

In the drawings, numeral 11 is a side edge of the base, numeral 12 is acover, numeral 13 is a test piece, numeral 14 is a hole to hang theprotective case, numeral 15 denotes air entrances provided on both sidesof the protective case, numeral 16 is a protruding portion to fix thecover 12 to the base 11, numeral 17 is a hole to be engaged with theprotruding portion 16 of the cover 12, and numeral 18 is a guide tofacilitate an air flow to the air entrance 15. The overall length of theprotective case is 90 mm, the overall width is 44 mm, and the overallheight is 30 mm.

Whereas the surface of the test piece 13 is covered with the cover 12,an operator's hand cannot directly contact the surface of the test piece13, however, the surface comes into contact with an environmental gasflowing through the air entrances 15.

Both ends of the test piece 13 are supported by side edges 11 of the setbase. When the protruding portions 16 of the cover 12 are engaged withthe holes 17 on both edges 11, the test piece 13 are fixed in the case.As shown in FIGS. 3D and 3E, the inner width W₁ of the set base isdesigned to be a little smaller than the outer width W₂ of the cover 12.Therefore, the cover 12 is preferably fixed to the base by thefrictional force generated between the cover 12 and both side edges 11.

The test piece 13 is fixed in parallel with the bottom surface of theset base 11 so that the surface (the main surface) of the test piece 13can be more contacted with air, and the air entrances 15 are disposed onthe right and left sides of the surface of the test piece 13. The airentrances 15 may be provided on either the base 11 or the cover 12 (oron both the base 11 and the cover 12). In general, at least the cover 12is made of transparent resin, and the air entrances 15 are provided onboth the base 11 and the cover 12.

In order to take in outside air as much as possible, the air entrances15 are preferably provided with guide (reflection plate: guide) 18.

Whereas the upper side of the main surface of the test piece 13 iscovered with the cover 12 as described above, water droplets can beprevented from dropping on the test piece 13. When this protective caseis hung from an eave, measurements can be performed outdoors. Especiallywhen the protective case is hung through the hole 14 formed on theprotective case, the main surface of the test piece 13 is approximatelyset in a vertical direction, so that the test piece can be protectedfrom rain. When this hole 14 is used, the protective case can be easilyhung even indoors.

This protective case can be preferably made by means of injectionmolding of transparent AS (acrylic styrene). In this case, polycarbonateresin can be also applied.

(3) Even the protective case shown in FIG. 3A can be used outdoors whenit is hung from an eaves. When an environmental atmosphere is measuredoutside of a building which has no eaves (or which has a small eaves) orin an open space without buildings such as a dry river bed, or when theprotective case is left under an eaves in the condition of a strongwind, the test piece gets wet in the rain.

In order to solve the above problems, an umbrella is attached to theprotective case.

Referring to FIGS. 4A to 4D, FIG. 4A is a perspective view of theprotective case (measuring kit) having an umbrella, FIG. 4B is alongitudinal sectional view of the protective case having an umbrella,and FIGS. 4C and 4D are development views showing the structure of theumbrella.

This umbrella is made of film-like organic material or sheet-likemetallic material. An umbrella portion 22 shown in FIG. 4C covers anupper portion of a sample 21 for measuring an environment. A ventilationhole 24 formed between the sample 21 and the umbrella portion 22 ismaintained at a position higher than the edge of the umbrella portion21. In the aforementioned manner, a sample fixing portion 23 shown inFIG. 4D is combined with the umbrella portion 22 as shown in FIG. 4A.The umbrella portions 21 and the sample fixing portion 23 are assembledin the aforementioned manner.

In this case, the sample 21 can be the protective case (measuring kit)itself shown in FIG. 3A, and this sample 21 is fixed to the samplefixing portion 23 by some means. The fixation can be performed by meansof a cord, frictional force, hook and the like.

When this umbrella is used as shown in FIGS. 4A and 4B, an upper portionof the sample 21 does not get wet in the rain being covered with theumbrella portion 22 disposed above the sample 21, and a side portion ofthe sample 21 does not get wet with the rain being covered with thesample fixing portion 23 disposed on the side of the sample. However,the air to be investigated can be ventilated by the air entrance 24provided between the sample and the umbrella. Therefore, the air issufficiently comes into contact with the sample. Whereas this airentrance is located at a position higher than the skirt of the umbrella,rain does not enter the air entrance.

Whereas the umbrellas of this type are made of sheet-shaped material,they can be mass-produced at low cost. Further, the produced umbrellascan be easily stored. Furthermore, they can be easily assembled, and thesamples can be easily attached to them. Therefore, the conventionalsamples can be applied to the umbrellas as they are. The sample andumbrella can be simply hung with a cord. However, since the skirt of thesample fixing portion is horizontal, the sample and umbrella may beplaced at a location where there is no rain water.

When at least a portion of the umbrella is made of transparent material,the color change of the sample can be observed at any time.

(4) In order to measure the average gas concentration over a long periodof time, test pieces are left in an environment for a predeterminedperiod of time, and then they are observed and analyzed. In some cases,it is desired to reduce the period of time in which the test pieces areleft in the environment. In order to accomplish the above object, theatmospheric air is forcibly sent to the test pieces so as to facilitatethe reaction between the environmental gas and the test pieces.

Therefore, the inventors have devised an apparatus by which fresh aircan be blown against the surface of a test piece when the protectivecase (measuring kit) shown in FIG. 3A is attached to the apparatus. Inthis case, air is blown by a fan. Alternatively, air may be sent to thetest piece when a convection is generated by heated air. From theviewpoint of safety and simplicity, the fan is advantageously used.

FIGS. 5A and 5B show the first embodiment. This embodiment isconstructed in the following manner: air is taken in from one side ofthe apparatus; the used air is discharged from the other side; and atest piece is disposed between the two sides.

FIG. 5A is a perspective view showing the outer appearance, and FIG. 5Bis a sectional view showing the horizontal section of the apparatus as amodel.

A dry battery 32 is attached to a measurement accelerating device 31. Inthis case, a solar battery may be used for the purpose of preventing theconsumption of the dry battery. Alternatively, an alternating currentpower source may be used. Then a motor 34 connected with the battery 32through a lead wire 33 is driven, and a fan 35 is rotated. When an uppercover 36 is set, the air taken in from an air entrance 37 is moved to anair outlet (referred to as an outlet hereinafter) 38, so that the air isblown out from the outlet 38 at a constant speed. The air speed can beadjusted when the speed of rotation of the motor 34 is changed. Thespeed of rotation of the motor 34 can be changed by a variable resistor39 connected with the lead wire in series.

The protective case 10 shown in FIG. 3A in which the test piece 13 isset, is attached to a case setting portion 40. The test piece is notdirectly set in the apparatus, but the protective case 10 is set, inwhich the test piece 13 is set as described above, which is effective inthat: the test piece can be easily handled; and the corrosion of thetest piece caused when an operator's hand carelessly comes into contactwith the test piece surface can be prevented. Whereas the case 10 isattached along a groove 41 formed in the case setting portion 40, it canbe horizontally fixed with respect to the measurement-accelerationdevice 31, so that the air flow can be maintained in parallel with thesurface of the test piece.

The air blown out from the outlet 38 enters the attached case 10 throughone of the air entrances 15 of the attached case 10, and comes intocontact with the surface of the test piece 13. After that, the air isdischarged from the other air entrance 15.

The test piece 13 reacts with gases contained in the introduced air, anda reaction peculiar to the combination of the test piece and the gasesis caused.

Materials used for the acceleration device body 31, upper cover 36 andfan 35 are selected from the organic materials such as acrylic resin,polycarbonate resin and polystyrene that cannot be corroded by gas.

The dry battery 32, lead wire 33, motor 34 and variable resistor 39 areprotected by measurement-acceleration device body 31 so that they cannotbe corroded by gas.

FIGS. 6A and 6B show the second embodiment in which air is verticallytaken in from an upper position and horizontally discharged, or air ishorizontally taken in and vertically discharged. FIG. 6A is aperspective view showing the appearance, and FIG. 6B is a longitudinalsectional view. Like parts in each of FIGS. 5A, 5B, 6A and 6B areidentified by the same reference character.

The case 10 shown in FIG. 3A is vertically set in the case settingportion 40 on the top of the apparatus.

An apparatus shown in FIGS. 7A, 7B and 7C is a variation of theapparatus shown in FIGS. 6A and 6B, and the battery 32 is disposed abovethe motor 34 and fan 35 so that the battery can be easily replaced whenthe cover 42 is opened, and further the weight and size of the apparatusare reduced, and furthermore the batteries are connected in parallel sothat the consumption of the batteries can be decreased.

FIG. 7A is a perspective view showing the appearance, FIG. 7B is alongitudinal sectional view, and FIG. 7C is an electrical circuitdiagram.

EXAMPLES Example 1

As shown in FIGS. 8A to 8C, porous test pieces of silver Ag and copperCu were made.

These test pieces 1 were formed into the size of 40 mm×5 mm×1 mmthickness from powder, the particle size of which was 50 μm, by means ofpress-forming. Next, these test pieces were sintered in a furnace, theatmosphere of which was substituted by hydrogen, at 500° C. for 2 hours,and porous sintered bodies, the densities of which were respectively 6.5g/cm³ and 6.8 g/cm³, were provided. In FIGS. 8B and 8C, numeral 4denotes copper particles, numeral 5 denotes voids, and numeral 6 denotesadsorbed NO_(x) gas.

In order to investigate the effect of collection of NO₂ gas, these testpieces were left in a desiccator into which NO₂ gas was introduced at aconcentration of 10 ppm, for 24 hours.

In order to make certain that the left test pieces had collected gas,they were analyzed with an infrared ray spectral analyzer and afluorescence X-ray analyzer.

An IR spectrum is shown in FIG. 9 in the case where the test pieces wereanalyzed by means of infrared ray spectral analysis. As can be seen inthe drawing, the known absorption wave-number of NO_(x) corresponds tothe wave-number obtained in this analysis. Therefore, it can be madecertain that the present test piece absorbed NO_(x) gas.

FIGS. 10 and 11 show the result of an analysis in which nitrogen andoxygen of the test pieces were analyzed with the fluorescence X-rayanalyzer. FIG. 10 shows the X-ray intensity of oxygen contained in theCu test piece provided in the fluorescence X-ray analysis. FIG. 11 showsthe X-ray intensity of nitrogen contained in the Cu test piece providedin the fluorescence X-ray analysis. From the results of the analysis, itcan be understood that oxygen and nitrogen are trapped in both testpieces.

As a test to put these test pieces into practical use, the present testpieces were left for one month in a desiccator into which NO₂ gas wasintroduced, the concentration of which was 10 ppb. While the test pieceswere left, they were taken out from the desiccator every five days, andthe X-ray intensity of nitrogen and that of oxygen were measured withthe fluorescence X-ray analyzer. As a result of the measurement, asshown in FIG. 12, NO₂ gas was not detected in the first stage since thetrap amount was small. However, the amounts of nitrogen and oxygenincreased until 25 days had passed from the start of measurement, and asufficient amount for analysis was trapped.

Example 2

In the same manner as that of Example 1, porous ceramic test pieces weremade of SiO₂ -xAl₂ O₃ (x=0.15) and YBa₂ Cu₃ Oy. These test pieces wereformed into the size of 40 mm×5 mm×1 mm thickness from powder, theparticle size of which was 50 μm, by means of press-forming. Next, thesetest pieces were sintered in a furnace, the atmosphere of which wassubstituted with hydrogen, at 1000° C. for 2 hours, and porous sinteredbodies, the densities of which were respectively 1.8 g/cm³ and 2.0g/cm³, were provided.

In order to investigate the effect of collection of NO₂ gas, these testpieces were left in a desiccator into which NO₂ gas was introduced at aconcentration of 10 ppm, for 24 hours.

In order to make certain that the left test pieces had collected gas,they were analyzed with the infrared ray spectral analyzer and thefluorescence X-ray analyzer.

The same result as that shown in FIG. 9 was provided in the case wherethe test pieces were analyzed by means of infrared ray spectralanalysis. As can be seen in the drawing, the known absorptionwave-number corresponds to the wave-number obtained in this analysis.Therefore, it can be made certain that the present test piece hadabsorbed NO_(x) gas.

The results of analysis of oxygen and nitrogen are the same as thoseshown in FIGS. 10 and 11, and it can be understood that oxygen andnitrogen are trapped in both test pieces.

As a test to put these test pieces into practical use, the present testpieces were left for one month in a desiccator into which NO₂ gas wasintroduced, the concentration of which was 10 ppb. In the same manner asthat of Example 1, the X-ray intensity of nitrogen and that of oxygenwere measured with the fluorescence X-ray analyzer. As a result of themeasurement, the same result as shown in FIG. 12 was provided, and NO₂gas was not detected in the first stage since the trap amount was small.However, the amounts of nitrogen and oxygen increased until 25 days hadpassed from the start of measurement, and sufficient amounts foranalysis were trapped.

Example 3

First, copper powder, the particle size of which was 100 μm, and SiO₂-xAl₂ O₃ (x=0.15), the particle size of which was 1 μm, was kneaded by aball mill, so that fine powder of SiO₂ -xAl₂ O₃ was attached onto thesurfaces of the copper particles. The copper powder was formed into thesize of 40 mm×5 mm×1 mm thickness by means of press-forming. Next, thetest piece was sintered in a furnace, the atmosphere of which wassubstituted with hydrogen, at 500° C. for 2 hours, and the test piecesmade of porous sintered bodies, the density of which was 4.0 g/cm³, wereprovided.

The inner structure of this test piece is shown in FIG. 13. Numeral 51denotes copper particles, numeral 52 denotes ceramic particles, andnumeral 53 denotes adsorbed nitrogen oxide.

The obtained test piece was left for 24 hours in a desiccator into whichNO₂ gas was introduced at a concentration of 10 ppm. The left test piecewas analyzed with the infrared ray spectral analyzer and thefluorescence X-ray analyzer. Both results provided by the infrared rayspectral analyzer and the fluorescence X-ray analyzer were the same asthose of Example 1.

As a test to put these test pieces into practical use, the present testpieces were left for one month in a desiccator into which NO₂ gas wasintroduced at a concentration of which was 10 ppb. In the same manner asthat of Example 1, the X-ray intensity of nitrogen and that of oxygenwere measured with the fluorescence X-ray analyzer. As a result of themeasurement, NO₂ gas was not detected in the first stage since the trapamount was small. However, the amounts of nitrogen and oxygen increaseduntil 25 days had passed from the start of measurement, and sufficientamounts for analysis were trapped.

Example 4

As shown in FIG. 14, a copper piece having a large number of holes wasmade by means of press-forming. The dimensions of the copper piece was40 mm×5 mm×1 mm thickness, and the diameter of the holes was 1 mm, andthe hole formation density was 25 holes/cm². Fine powder of SiO₂ -xAl₂O₃ (particle size: 10μ) was charged into these holes.

Charging of the powder was performed in the following manner:

Powder of SiO₂.Al₂ O₃ was previously scattered over the test piecehaving holes so that the powder was put into the holes. Then, residualpowder was removed from the test piece surface. Next, for the purpose offixing the powder, the test piece was fired at 500° C. in a hydrogenatmosphere for 2 hours. In FIG. 14, numeral 55 is a copper piece, andnumeral 56 is a fine ceramic particle charged into the hole of thecopper piece.

The present test piece was left for 24 hours in a desiccator into whichNO₂ was introduced at a concentration of 10 ppm. The left test piece wasanalyzed with the infrared spectral analyzer and the fluorescence X-rayanalyzer. As a test to put the test piece into practical use, thepresent test piece was left for one month in a desiccator into which NO₂gas was introduced at a concentration of 10 ppb. The X-ray intensity ofnitrogen and that of oxygen were measured with the fluorescence X-rayanalyzer.

The same result as that of Example 1 was provided.

Example 5

First, SiO₂ -xAl₂ O₃ of which the particle size was 100 μm and Cu powderof which the particle size was 1 μm were kneaded with a ball mill sothat Cu powder was attached onto the surfaces of the particles of SiO₂-XAl₂ O₃. This ceramic powder was formed into a piece of which the sizewas 40 mm×5 mm×1 mm thickness, then the piece was sintered at 1000° C.for 2 hours in a furnace of which the atmospheric gas was substituted byhydrogen, so that a test piece made of a sintered body of which thedensity was 2.4 g/cm² was provided.

The present test piece was left for 24 hours in a desiccator into whichNO₂ gas was introduced at a concentration of 10 ppm. The left test piecewas analyzed with the infrared spectral analyzer and the fluorescenceX-ray analyzer. As a test to put the test piece into practical use, thepresent test piece was left for one month in a desiccator into which NO₂gas was introduced at a concentration of 10 ppb. The X-ray intensity ofnitrogen and that of oxygen were measured with the fluorescence X-rayanalyzer.

The same result as that of Example 1 was provided.

Example 6

As shown in FIG. 14, a ceramic piece having a large number of holes wasmade by means of press-forming. The dimensions of the ceramic piece was40 mm×5 mm×1 mm thickness, and the diameter of the holes was 1 mmφ, andthe hole formation density was 25 holes/cm². Fine powder of Cu wasscattered over the test piece having holes so that the powder was putinto the holes. Then, residual powder was removed from the test piecesurface. Next, for the purpose of fixing the powder, the test piece wasfired in a furnace with a hydrogen atmosphere for 2 hours at 500° C. InFIG. 14, numeral 55 is a ceramic piece, and numeral 56 is Cu powdercharged into the holes in the ceramic piece.

The present test piece was left for 24 hours in a desiccator into whichNO₂ was introduced at a concentration of 10 ppm. The left test piece wasanalyzed with the infrared spectral analyzer and the fluorescence X-rayanalyzer. As a test to put the test piece into practical use, thepresent test piece was left for one month in a desiccator into which NO₂gas was introduced at a concentration of 10 ppb. The X-ray intensity ofnitrogen and that of oxygen were measured with the fluorescence X-rayanalyzer.

The same result as that of Example 1 was provided.

Example 7

In the same manner as that shown in Example 1, a porous test piece of Cuwas made. This test piece was made of Cu powder of which the particlesize was 50 μm, and formed into a piece of 40 mm×5 mm×1 mm thickness bymeans of press-forming. Next, this piece was sintered at 500° C. for 2hours in a furnace, the atmospheric gas of which was substituted byhydrogen, so that a porous sintered body of which the density was 6.8g/cm³ was provided. Next, this copper piece was dipped intriethanolamine for 24 hours, so that the copper piece was sufficientlypermeated with triethanolamine.

The present test piece was left for 24 hours in a desiccator into whichNO₂ was introduced at a concentration of 10 ppm. The test piece wasanalyzed with the infrared spectral analyzer and the fluorescence X-rayanalyzer. As a test to put the test piece into practical use, thepresent test piece was left for one month in a desiccator into which NO₂gas was introduced at a concentration of 10 ppb. The x-ray intensity ofnitrogen and that of oxygen were measured with the fluorescence X-rayanalyzer.

The same result as that of Example 1 was provided.

Example 8

As shown in FIGS. 8A to 8C, a porous test piece of Tb₂ O₃ was made. Thistest piece was made of powder of which the particle size was 50 μm, andformed into a piece of 40 mm×5 mm×1 mm thickness by means ofpress-forming. Next, this piece was sintered at 500° C. for 2 hours in afurnace, the atmospheric gas of which was substituted by hydrogen, sothat a porous sintered body of which the density was 2.7 g/cm³ wasprovided.

In order to investigate the effect of collection of CO₂ gas, the testpiece was left in a desiccator into which CO₂ gas was introduced at aconcentration of 10 ppm, for 100 hours.

In order to investigate whether or not the test piece had adsorbed CO₂gas, the test piece was analyzed with the XPS. As a result of the test,it was found that 4 conditions [CO₃, CO₂, CO, (C--C, C--H)] existed inthe C-1s spectrum shown in FIG. 15. Therefore, it was confirmed that CO₂gas existed.

As a test to put this test piece into practical use, the test piece wasleft for 1 month in a desiccator into which CO₂ gas was introduced at aconcentration of 10 ppm. While the test piece was left, it was taken outfrom the desiccator every 10 days and subjected to quantitative analysisusing XPS.

The experiment was continued. As a result, as shown in FIG. 16, theamount of CO₂ increased with the lapse of time, so that a sufficientamount of CO₂ for analysis was trapped.

The same investigation was made using Eu₂ O₃, Gd₂ O₃, Tb₂ O₃, Tb₄ O₇,Dy₂ O₃ and Ho₂ O₃. As a result, as shown in FIG. 17, the same adsorptionresult as that of the case in which Tb₂ O₃ was used was provided.

Example 9

As described above, it was found that specific chlorides, for example,CuCl and AgCl were effective as collecting material (a test piece) forselectively collecting SO₂. Since the test piece must be handled by anumber of operators at various places, the durability and the adherencebetween a compound and a base material are required. Therefore, metalwas selected for the base material. Next, the test piece manufacturingmethod was investigated so that the adherence between the metal and acompound could be improved. The various investigated methods are shownas follows.

(1) A powder-like compound is pressed into a piece and adhered onto asurface of metal with adhesive.

(2) A powder-like compound and powder-like metal are mixed and pressedinto a piece.

(3) The compound is generated on a metal surface in the form of corrodedsubstance.

The following results were provided:

In the case of the test piece made by the method (1), compound tends tocollapse and return to the original condition. In the case of the testpiece made by the method (2), compound is embedded in the metal, and thesurface of the test piece is covered with metallic oxide, which preventscompound from becoming sulfate. For this reason, it was found that themethods (1) and (2) are not effective. On the other hand, it was foundthat the following method based on (3) is effective.

It has been known that metal corrodes in a chloride gas atmosphere. Theinventors found that: in a chloride gas atmosphere, especially in a drycondition (the humidity is not more than 10% RH), only CuCl is formed onthe surface of copper, and only AgCl is formed on the surface of silver.Utilizing this corrosive reaction, the inventors made a test piece usingthe following process.

(1) An apparatus for diluting gas stably and a container for equalizingthe diluted gas are prepared, and an atmosphere of dry chloride gas, theconcentration of which is 10 ppm, is made.

(2) Oxide and a rust preventive agent on the surfaces of copper andsilver sheets (40×5×0.3 mm) are removed by grinding with a grindingwheel, and in order to remove the polished powder, the sheets aresubjected to ultrasonic cleaning in which alcohol or acetone is used.

(3) These copper and silver sheets are left in the atmosphere made inthe process (1).

(4) After left for 40 hours, the silver and copper sheets, on thesurface of which AgCl and CuCl are formed are taken out.

(5) The silver and copper sheets taken out are accommodated in the caseshown in FIG. 3A. In order to prevent the degeneration of AgCl and CuClon the surface, the Ag and Cu sheets are stored in a dry nitrogenatmosphere until the sheets are left in an actual environment.

Using the test piece (measuring kit) made in the aforementioned manner,it was made certain that SO₂ gas could be substantially collected.Therefore, 15 types of atmospheres were made, in which the humidity wasset at 10, 30, 50, 70 and 90% RH, and SO₂ concentration was set at 1ppm, 100 ppb and 10 ppb. The test pieces were left in the aboveatmospheres for one month. After that, the test pieces were checked bythe following method.

(1) Confirmation by the X-ray microanalyzer (XMA)

Using the XMA, each element can be subjected to qualitative andquantitative analyses. In the case where the metal surfaces of thecollection kit left in the SO₂ gas environment were changed to Ag₂ SO₃,Ag₂ SO₄ and CuSO₄, oxygen (O) and sulfur (S) must be detected.Therefore, qualitative analysis was made. According to the analysis, thefollowing results were provided in any humidity condition.

    ______________________________________                                        Results of Qualitative Analysis Made by XMA                                   Com-                                                                          pound                                                                         on                                                                            Test     1 ppm           100 ppb     10 ppb                                   Piece    o     S         o   S       o   S                                    ______________________________________                                        AgCl     o     o         o   o       o   o                                    CuCl      o    o         o   o       o   o                                    ______________________________________                                         (Remark) o: Existence was confirmed.                                     

After that, an atmosphere of H₂ S or an atmosphere of NO₂, theconcentration and humidity of which were the same as those of theatmosphere of SO₂, were made, and the same confirmation tests werecarried out. The result was as follows: only when the humidity was 70and 90% RH, O was confirmed in the test piece, the compound of which wasCuCl. The above result was obtained because the standard formationenergy of CuCl and that of CuO were approximately the same, and metalwas oxidized due to the water contained in the humid atmosphere.Therefore, the principle of collection agrees with the substantialexperimental result, so that the appropriateness of the presentinvention was proved.

(2) Confirmation by X-ray diffraction (XD)

According to the X-ray diffraction, the product on the metal surface canbe identified. Accordingly, it was confirmed that Ag₂ SO₃, Ag₂ SO₄ andCUSO₄ were substantially produced on the metal surface of the test pieceleft in the gas environment. As a result, the existence of a productsimilar to sulfate shown here was confirmed in 2 types of test pieces inany environment.

(3) Making a calibration curve

In the qualitative analysis conducted by the XMA, amounts of S atomswere investigated with respect to the test pieces left under these 15conditions.

As a result, whereas it was found that the amounts of S atoms of CuCland AgCl samples were constant, a relation between the concentration ofSO₂ and the amount of S atoms was made clear. Therefore, the calibrationcurve could be made.

A calibration curve, for a test piece of which is made of AgCl, is shownin FIG. 18.

The test piece was measured by both the conventional method (JIS K-0103)and the method of the present invention in which the test piece was leftand the SO₂ gas concentration was measured, and the obtained resultswere compared. The following tables show the results of the test.

    ______________________________________                                        Measured Area "A" (Industrial Area)                                                        SO.sub.2 concentration (ppb)                                     ______________________________________                                        Conventional Method                                                                          83                                                             Present Invention                                                                                            80                                             ______________________________________                                    

    ______________________________________                                        Measured Area "B" (Residential Area)                                                       SO.sub.2 concentration (ppb)                                     ______________________________________                                        Conventional Method                                                                          26                                                             Present Invention                                                                                             30                                            ______________________________________                                    

    ______________________________________                                        Measured Area "C" (Overseas)                                                               SO.sub.2 concentration (ppb)                                     ______________________________________                                        Conventional Method                                                                          46                                                             Present Invention                                                                                              50                                           ______________________________________                                    

In the case of test pieces of CuCl, the same result was provided.

As a result of the experiments, it was confirmed that the same values asthose of the conventional test pieces were provided by these testpieces.

As can be seen from the examples described above, SO₂ could be collectedby these test pieces. After the test pieces had been left in anenvironment, the gas concentration of which was changed, the test pieceswere subjected to quantitative analysis, and the calibration curve wasmade. Therefore, these test pieces can be applied to actualmeasurements.

Example 10

For the purpose of investigating the effect of an umbrella to which thetest piece 13 for measuring the environmental gas (when the test pieceis set in a case, it is referred to as a test piece kit) was applied asa simple type environment measuring sample wherein the test piece 13 formeasuring the environmental gas was set in the protective case 10 shownin FIG. 3A, an environmental investigation was made outside an ordinaryhouse located in a city area. In this experiment, Cu, Ag, Al, Fe andFe--Ni were used for the test pieces. Three test piece kits wereprepared, and the first set of them was hung from the inside of a largeeave with a cord inserted into the hole 14 formed on the case so thatthe test piece kits did not get wet with rain. The second set wasprovided with an umbrella of the invention and hung from a clothes polein a yard facing the eaves. The third set was hung from the clothes poleas it was. Roofs were not provided above the clothes pole, so that thesecond and third sets were exposed to the rain.

In this connection, the hole 14 of the umbrella may be sealed with clayand other materials if necessary.

These test piece kits were left for one month. While the test piece kitswere left, it rained several times. After a predetermined period of timehad passed, the X-ray intensities of oxygen O, sulfur S and chloride Clin the corrosive product formed on each test piece were measured withthe fluorescence X-ray analyzer. The results of the experiment are shownin FIGS. 19A, 19B, and 19C. In the case of the sample without a roof andan umbrella, since the air entrance 15 of the case was provided upward,the rain water entered the case from the air entrance 15, and came intocontact with the sample. Accordingly, as shown in FIGS. 19A to 19C, thesamples were remarkably corroded by the rain water, which is a corrosionfactor except for gas, as compared with the sample hung from the eaves.Further, since Cl was deposited together with the rain water, accuratevalues were not provided. However, an amount of corrosion of the samplehung from the eaves and that of the sample provided with the umbrellawere approximately the same. That is, it was confirmed that the sampledid not get wet with the rain because of the umbrella, and a sufficientamount of air was supplied to the sample, so that the gas measurementwas accurately performed.

Example 12

In order to confirm the effects of the apparatus shown in FIGS. 5A and5B, two types of apparatus were prepared. One was an apparatus providedwith a dry battery so as to investigate a relation between the windspeed above the test piece and the reactivity of the gas and test piece,and the wind speed above the test piece was set to be each of 0.1, 0.2,0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 m/s. The other was anapparatus not provided with a dry battery. In this case, test pieces ofsilver Ag were prepared, as silver Ag remarkably reacts with hydrogensulfide H₂ S, and S compounds are generated on the surface. The testpieces of silver Ag were accommodated in the cases, wherein 11 sets oftest pieces were prepared so as to be assembled to each apparatus. H₂ Sgas was introduced into each set by the concentration of 10 ppm. Eachset was left for 2 weeks in a desiccator, the temperature of which was20° C. and the humidity of which was 80%. After that, each test piecewas analyzed. The fluorescence X-ray analyzer was used for the analysis,and the X-ray intensity of S contained in the compound produced on theAg surface was measured.

The results are shown in FIG. 20.

Since the X-ray intensity represents an amount of S, the following wasproved by FIG. 20:

In the case where gas was supplied at a certain speed and came intocontact with the surface of a test piece, an amount of reaction causedbetween the gas and the test piece was increased as compared with a casein which the test piece was left as it was. Further, a reaction causedbetween Ag and H₂ S was most facilitated at a certain wind speed, andthe wind speed was 0.8 m/s.

Next, two sets of Ag test pieces provided in a case were prepared. Oneof them was left being not assembled to an apparatus, and the other wasassembled to an apparatus in which the wind speed of the upper portionof the test piece was set to be 0.8 m/s. Under the aforementionedcondition, the test pieces were left in a desiccator into which H₂ S gaswas introduced by the concentration of 10 ppm, and the temperature inthe desiccator was maintained at 20° C. and the humidity was maintainedat 80%. The test pieces were taken out from the desiccator at varioustimes and the X-ray intensity of S was measured.

The result of the experiment is shown in FIG. 21. As shown in thedrawing, in three weeks, the amount of reaction caused between Ag and Sin the case assembled to the apparatus reached an amount of reactioncaused between Ag and S for one month in the case not assembled to theapparatus. Consequently, it was confirmed that this apparatus has theeffect of facilitating the reaction caused between the gas and testpiece.

Example 13

In order to make certain of the effect of the apparatus shown in FIGS.6A and 6B, in the same manner as that of Example 11, two sets of Ag testpieces provided in a case were prepared. One of them was left being notassembled to an apparatus, and the other was assembled to an apparatusin which the wind speed of the upper portion of the test piece wasadjusted to be 0.8 m/s by the variable resistor 39 in accordance withthe result shown in FIG. 20. Under the aforementioned condition, thetest pieces were left in a desiccator into which H₂ S gas was introducedby the concentration of 10 ppm, and the temperature in the desiccatorwas maintained at 20° C. and the humidity was maintained at 80%. Thetest pieces were taken out from the desiccator at various times andX-ray intensity of S was measured.

The result of the experiment is shown in FIG. 22.

As shown in the drawing, in two weeks, an amount of reaction causedbetween Ag and S in the case assembled to the apparatus reached anamount of reaction caused between Ag and S for one month in the case notassembled to the apparatus. Consequently, it was confirmed that thisapparatus has the effect of facilitating the reaction caused between thegas and test piece.

In Example 12, the construction of Example 11 was improved since it wasdisadvantageous in that gas was trapped by the inner walls and the fanas the air entrance is distant from the case. As a result of theimprovement, the reaction was effectively facilitated.

Example 14

The effect of the apparatus shown in FIGS. 7A, 7B and 7C was determinedin the following manner. One set of apparatus provided with the drybattery 32 was prepared, so that the wind speed in the upper position ofthe test piece was adjusted to be 0.15, 0.25, 0.45, 0.65, 1.00 and 1.30m/s, and two sets of apparatus not provided with the dry battery 32 wereprepared. In this connection, one of the apparatus is referred to as(1), and the other is referred to as (2). Test pieces of copper Cu andsilver Ag were prepared, which remarkably react with hydrogen sulfide sothat compounds of sulfur S are produced on the surface. Then, a set oftest pieces Cu and Ag were accommodated in a case. Then, 8 sets of testpieces, each set including Cu and Ag test pieces, were prepared andrespectively assembled to the apparatus. The sets of test pieces exceptfor (2) were left for 2 weeks in a desiccator into which H₂ S gas wasintroduced at a concentration of 100 ppb, and the temperature in thedesiccator was maintained at 25° C. and the humidity was maintained at60%. The sets of test pieces in (2) were left in the desiccator for onemonth. After that, each test piece was analyzed. For the analysis, thefluorescence X-ray analyzer was used, and the X-ray intensity of Scontained in the compounds produced on the surfaces of Cu and Ag wasmeasured.

The results are shown in FIGS. 23 and 24. The X-ray intensity representsthe amount of S. As can be seen from FIGS. 23 and 24, when a wind wasblown against the test pieces by this apparatus at a speed of 0.15 m/sfor 2 weeks, the same corrosion amount as that of the test pieces leftfor one month in the conventional manner was provided.

The apparatus of Example 13 is characterized in that: the dry batteriesare connected in parallel in order to reduce the consumption of the drybatteries; and consideration is given to the layout of parts in theapparatus, and the size and weight of the apparatus are reduced so thatthe dry batteries can be easily attached to and detached from theapparatus. Also, when the reduced period in which the test piece is leftis determined to be 2 weeks, and the wind speed is determined to be 0.15m/sec, the same corrosion amount as that of the test piece that has beenleft for one month can be provided. Therefore, the operational data ofthe apparatus of the present invention corresponds to the dataaccumulated in the past, so that the conventional data can beeffectively utilized.

[Industrially Applicable Possibility]

The apparatus of the present invention can be made compact and producedat low cost. Further, the apparatus is capable of simply monitoring anaverage concentration of specific gas (especially, NO_(x), CO₂, and SO₂gas) in an environment over a long period of time at an arbitrarylocation. Accordingly, the apparatus of the present invention can beapplied to the measurement of environmental pollution which has recentlybecome a problem to be solved and, further, can be applied to theevaluation of an environment in which precision machines and electronicequipment are installed.

We claim:
 1. A kit for collecting an environmental sample from anenvironmental atmosphere for use in determining, from the collectedenvironmental sample, respective concentrations of NO_(x), CO₂ or SO₂ inthe environmental atmosphere, the kit comprising:a test piece made of ametal, a ceramic or a metallic salt material, having an exposed surfaceand a porous structure in at least a layer including the exposed surfaceand selectively adsorbing NO_(x), CO₂ or SO₂ gas in the environmentalatmosphere; and a case disposing the test piece in the environmentalatmosphere to collect the environmental sample.
 2. The kit according toclaim 1 wherein, for use in determining the concentration of CO₂contained in the environmental atmosphere, said test piece is made of aporous metallic oxide material selected from La₂ O₃, Ce₂ O₃, Pr₂ O₃, Nd₂O₃, Pm₂ O₃, Sm₂ O₃, Eu2O₃, Gd₂ O₃, Tb₂ O₃, Tb₃ O₇, Dy₂ O₃, Ho₂ O₃, Er₂O₃, Tm₂ O₃, and Yb₂ O₃ materials.
 3. The kit according to claim 1wherein, for use in determining the concentrations of at least two ofNO_(x), CO₂ and SO₂, said kit includes not less than 2 of said testpieces.
 4. The kit according to claim 1, wherein the test piece collectsan environmental gas sample of one of NO_(x), CO₂ or SO₂ environmentalgases in an amount or at a rate, over a selected time duration and inrelation to the concentration of the environmental gas in theenvironmental atmosphere, so that the test piece on which the gas iscollected can be used to determine the average concentration of thecollected gas in the environmental atmosphere over the selected timeduration.
 5. The kit according to claim 1, wherein the density of aporous ceramic structure is not more than 2 grams per cm³.
 6. The kitaccording to claim 1, wherein the test piece is made of a brass-basedmetal having an internal stress of at least approximately 100 MPa. 7.The kit according to claim 1, wherein the porous structure of asurrounding material comprises fine ceramic powder having a particlesize of from 0.05 μm to 5 μm.
 8. The kit according to claim 1, whereinthe NO_(x), CO₂ or SO₂ gas is absorbed on the exposed surface of themetal or the ceramic material and reacts with but is not absorbed by thecopper chloride or silver chloride material.
 9. The kit according toclaim 1 wherein, for use in determining the concentration of SO₂contained in the environmental atmosphere, said test piece is made of ametal chloride material which has a free formation energy of chloridelarger which is than a free formation energy of sulfate.
 10. The kitaccording to claim 9, wherein said metallic chloride material is aselected one of copper chloride and silver chloride materials.
 11. Thekit according to claim 9, wherein the NO_(x), CO₂ or SO₂ gas is absorbedon the exposed surface of the metal or the ceramic material and reactswith but is not absorbed by the copper chloride or silver chloridematerial.
 12. The kit according to claim 1, wherein the porous structurecomprises sintered metallic particles or ceramic powder.
 13. The kitaccording to claim 12, wherein the density of a porous structure is notmore than 7 grams per cm³.
 14. The kit according to claim 1, whereinsaid test piece is made of a porous metal material or a porous ceramicmaterial on which a layer of fine metallic particles or a layer ofceramic powder, respectively, is carried, or of a solid metal materialor a solid ceramic material on which a layer of fine metallic particlesor a layer of ceramic powder, respectively, is carried.
 15. The kitaccording to claim 14 wherein, for use in determining the concentrationof NO_(x) in the environmental atmosphere, said porous ceramic materialor said layer of particulate ceramic is a selected one of SiO₂ -Al₂ O₃,YBa₂ Cu₃ O_(x), CrO₂, Cr₂ O₃, Fe₂ O₃, Co₂ O₃, SnO₂, CoAl₂ O₄, CuO, Al₂O₃, and MgO materials.
 16. The kit according to claim 14 wherein, foruse in determining the concentration of NO_(x) contained in theenvironmental atmosphere, said test piece is made of a porous metalmaterial or a porous ceramic material, each having voids therein filledwith triethanolamine.
 17. The kit according to claim 14, wherein thetest pieces have metallic particle sizes in the range from 30 μm to 200μm.
 18. The kit according to claim 14 wherein, for use in determiningthe concentration of NO_(x) in the environmental atmosphere, said porousmetal material or said layer of fine metallic particles is a selectedone of copper, silver, platinum, rhodium, ruthenium, palladium, iridiumand nickel materials.
 19. The kit according to claim 18, wherein theselected metal material is copper.
 20. A kit for collecting anenvironmental sample from an environmental atmosphere for use indetermining, from the collected environmental sample, a concentration ofat least one of NO_(x), CO₂ and SO₂ contained in the environmentalatmosphere, the kit comprising:a test piece made of a metal, a ceramicor a metallic salt material having an exposed surface and a porousstructure in at least a layer including the exposed surface andselectively adsorbing NO_(x), CO₂ or SO₂ gas in the environmentalatmosphere, the test piece being made of at least one of:i) porous metalor porous ceramic, or solid metal or solid ceramic on a surface of whicha layer of fine metallic particles or a layer of ceramic powder,respectively, are carried, the metal of the porous metal or of the finemetallic particles layer being selected from the group consisting ofcopper, silver, platinum, rhodium, ruthenium, iridium and nickel, theceramic of the porous ceramic or of the ceramic powder layer beingselected from the group consisting of SiO₂ --Al₂ O₃, YBa₂ Cu₃ O_(x),CrO_(z), Cr₂ O₃, Fe₂ O₃, Co₂ O₃, SnO₂, CoAl₂ O₃, CuO, Al₂ O₃ and MgO;ii) a porous metal or a porous ceramic, each having voids therein whichare filled with triethanolamine, for collecting a sample for use indetermining the concentration of NO_(x) ; iii) a porous oxide of a rareearth metal selected from the group consisting of La₂ O₃, Ce₂ O₃, Pr₂O₃, Nd₂ O₃, Pm₂ O₃, Sm₂ O₃, Eu₂ O₃, Gd₂ O₃, Tb₂ O₃, Tb₃ O₇, Dy₂ O₃, Ho₂O₃, Er₂ O₃, Tm₂ O₃ and Yb₂ O₃ for collecting a sample for use indetermining the concentration of CO₂ ; and iv) copper chloride or silverchloride for collecting a sample for use in determining theconcentration of SO₂.
 21. The kit according to claim 20 wherein, for usein determining the concentrations of at least two of NO_(x), CO₂ andSO₂, said kit includes not less than 2 of said test pieces.
 22. The kitaccording to claim 20, wherein the test piece collects an environmentalgas sample of one of NO_(x), CO₂ or SO₂ environmental gases in an amountor at a rate, over a selected time duration and in relation to theconcentration of the environmental gas in the environmental atmosphere,so that the test piece on which the gas is collected can be used todetermine the average concentration of the collected gas in theenvironmental atmosphere over the selected time duration.
 23. A kit forcollecting an environmental sample from an environmental atmosphere thecollected environmental sample affording a basis for determiningrespective concentrations of NO_(x), CO₂ or SO₂ in the environmentalatmosphere, the kit comprising:a test piece made of a metal, a ceramicor a metallic salt material of copper chloride or silver chloride,having an exposed surface and a porous structure in at least a layerincluding the exposed surface NO_(x), CO₂ or SO₂ gas in theenvironmental atmosphere; and a case disposing the test piece in theenvironmental atmosphere to collect the environmental sample.
 24. Thekit according to claim 23, wherein the NO_(x), CO₂ or SO₂ gas isabsorbed on the exposed surface of the metal or the ceramic material andreacts with but is not absorbed by the copper chloride or silverchloride material.
 25. A kit for collecting an environmental sample froman environmental atmosphere the collected environmental sample affordinga basis for determining a concentration of at least one of NO_(x), CO₂and SO₂ contained in the environmental atmosphere, the kit comprising:atest piece made of a metal, a ceramic or a metallic salt material havingan exposed surface and a porous structure in at least a layer includingthe exposed surface, the test piece being made of at least one of:i)porous metal or porous ceramic, or solid metal or solid ceramic on asurface of which a layer of fine metallic particles or a layer ofceramic powder, respectively, are carried, the metal of the porous metalor of the fine metallic particles layer being selected from the groupconsisting of copper, silver, platinum, rhodium, ruthenium, iridium andnickel, the ceramic of the porous ceramic or of the ceramic powder layerbeing selected from the group consisting of SiO₂ --Al₂ O₃, YBa₂ Cu₃O_(x), CrO_(z), Cr₂ O₃, Fe₂ O₃, Co₂ O₃, SnO₂, CoAl₂ O₃, CuO, Al₂ O₃ andMgO; ii) a porous metal or a porous ceramic, each having voids thereinwhich are filled with triethanolamine, for collecting a sample for usein determining the concentration of NO_(x) ; iii) a porous oxide of arare earth metal selected from the group consisting of La₂ O₃, Ce₂ O₃,Pr₂ O₃, Nd₂ O₃, Pm₂ O₃, Sm₂ O₃, Eu₂ O₃, Gd₂ O₃, Tb₂ O₃, Tb₃ O₇, Dy₂ _(O)₃, Ho₂ O₃, Er₂ O₃, Tm₂ O₃ and Yb₂ O₃ for collecting a sample for use indetermining the concentration of CO₂ ; iv) copper chloride or silverchloride for collecting a sample for use in determining theconcentration of SO₂.
 26. The kit according to claim 25, wherein theNO_(x), CO₂ or SO₂ gas is absorbed on the exposed surface of the metalor the ceramic material and reacts with but is not absorbed by thecopper chloride or silver chloride material.